Fluorine-containing photosensitive polymer having hydrate structure and resist composition comprising the same

ABSTRACT

Provided are a fluorine-containing photosensitive polymer having a hydrate structure and a resist composition including the photosensitive polymer. The photosensitive polymer has an average molecular weight of about 3,000-100,000 with a repeating unit including a group having one of structural formulae below:

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photosensitive polymer and a chemically amplified resist composition, and more particularly, to a fluorine-containing photosensitive polymer and a resist composition including the photosensitive polymer.

2. Description of the Related Art

As the manufacture of semiconductor devices becomes complicated and the integration density of semiconductor devices increases, there is a need to form a fine pattern. Furthermore, with regard to semiconductor devices of 1-Gigabit or greater, a pattern size having a design rule of 0.1 μm or less is needed. However, when a conventional photoresist material is exposed with KrF excimer laser (248 nm), there is a limitation in forming such fine patterns. For this reason, a lithography technique using a new exposure light source, ArF excimer laser (193 nm), has emerged, and the focus of the research on ArF resist compositions has been on acrylic polymers and COMAs (cycloolefin-maleic anhydrides).

For a smaller pattern size, there is extensive focus on lithography using short-wavelength generating F₂ (157 nm) excimer laser. Conventional KrF or ArF resists are unsuitable for use with the short-wavelength source of 157 nm due to their low transmittance. Therefore, a polymer with a novel structure which is transparent to a157-nm wavelength is more suitable. A chemical component dissolvable in developer includes phenol, carboxylic acid, α-fluorocarbon-substituted alcohol, and hydroxy silane having a structure of formula 1 below:

Among these components, phenol and carboxylic acid have a very poor transmittance with respect to 157-nm beam. Whereas α-fluorocarbon-substituted methanol and hydroxy silane are relatively more transparent at a wavelength of 157-nm. As a result, interest in studying α-fluorocarbon-substituted methanol and hydroxy silane has increased.

According to recent research data, appropriate substitution of a phenolic or carboxylic derivative with fluorine is found to be effective for transmittance and contrast enhancement, suggesting its use as a polymer for a 157-nm exposure source (Journal of Photopolymer Science and Technology, Vol. 14, No. 4, 583-593, 2001; Journal of Photopolymer Science and Technology, Vol. 14, No. 4, 669-674, 2001).

Structures of fluorine-substituted photosensitive polymers for conventional resist compositions are shown in formula 2 below.

Despite the existence of the ether group in those structures of formula 2 above, advantages of a high transmittance due to the acrylate polymer and of their ease of preparation has increased use of those structures substituted with fluorocarbon to an appropriate degree. t-butyl trifluoromethyl acrylate is widely used as a monomer for enhancing contrast. An aromatic hydrocarbon monomer having a low transmittance at 157-nm can be changed into a hexafluoroisopropanol-substituted styrene structure with enhanced transmittance to be suitable as a resist material.

In addition, extensive research into resist compositions derived from acrylate polymers, non-carboxylic fluorinated vinyl ether polymers, and polymers with cyclic ether in their main chain, and copolymers of tetrafluoroethylene and norbornene derivatives known to be highly transparent at 157-nm, having structures of formula 3 below, are in progress.

In formula 3 above, R may be a methyl group, a t-butyl group, an adamantly group, a trifluoromethylnorbornyl group, or a hexafluoroisopropyl group.

A fluorinated polymer has excellent transmittance at 157-nm when it contains more fluorine atoms, but its enhanced hydrophobicity degrades adhesion to an underlayer. To date, resist materials having a suitable structure for 157-nm laser have not been found. Therefore, there is a need for a polymer having a high transmittance at 157-nm and without the aforementioned problems and thus be suitable as a resist material for F₂ excimer laser.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a photosensitive polymer having a structure to give a high transmittance at a F₂ excimer laser wavelength of 157 nm and good adhesion to an underlayer.

It is another object of the present invention to provide a resist composition allowing development with conventional developers and having a high transmittance at a F₂ excimer laser wavelength of 157 nm, good hydrophilicity, and good adhesion to an underlayer.

According to an aspect of the present invention, a photosensitive polymer is provided having an average molecular weight of about 3,000-100,000 with a repeating unit including a group of one of the structures of formula 4 below:

In the photosensitive polymer, the repeating unit may have a structure of formula 5 below:

where n is 0 or 1, and R₁ is a substituted or unsubstituted C₁-C₅ hydrocarbon group.

The repeating unit of formula 5 above may be derived from a monomer of formula 6 below:

Alternatively, the repeating unit constituting the photosensitive polymer according to an embodiment of the present invention may have a structure of formula 7 below:

where n is 0 or 1, and R₂ is a substituted or unsubstituted C₁-C₅ hydrocarbon group.

The repeating unit of formula 7 above may be derived from a monomer of formula 8 below:

Alternatively, the repeating unit constituting the photosensitive polymer according to an embodiment of the present invention may have a structure of formula 9 below:

where n is 0 or 1, and R₃ is a substituted or unsubstituted C₁-C₅ hydrocarbon group.

The repeating unit of formula 9 above may be derived from a monomer of formula 10 below:

Alternatively, the repeating unit constituting the photosensitive polymer according to an embodiment of the present invention may have a structure of formula 11 below:

where R₄ is a substituted or unsubstituted C₁-C₅ hydrocarbon group.

The repeating unit of formula 11 above may be derived from a monomer of formula 12 below:

Alternatively, the repeating unit constituting the photosensitive polymer according to an embodiment of the present invention may have a structure of formula 13 below:

The repeating unit of formula 13 above may be derived from a monomer of formula 14 below:

According to a second embodiment of the present invention, a photosensitive polymer is provided having an average molecular weight of about 3,000-100,000 with a first repeating unit having one group of a structure selected from formula 4 above and at least one second repeating unit selected from the group consisting of acrylate, methacrylate, maleic anhydride, norbornene, styrene, tetrafluoroethylene, and sulfur dioxide derivatives.

Alternatively, the photosensitive polymer according to the second embodiment of the present invention may have a structure of formula 15 below:

where n is 0 or 1; R₁ is a substituted or unsubstituted C₁-C₅ a hydrocarbon group; R₅ is hydrogen atom, a methyl group, or a trifluoromethyl group; R₆ is a hydrogen atom or a substituted or unsubstituted C₁-C₂₀ hydrocarbon group; and R₇ is hydrogen atom, a hydroxyl group, a nitrile group, a substituted or unsubstituted C₁-C₁₂ alkyl group, a fluorinated C₁-C₁₂ alkyl group, an alkoxy group, or an ester group. Preferably, R₆ is a C₄-C₁₂ acid-labile group, and more preferably, a t-butyl group. Preferably, R₇ is a fluorinated C₃-C₁₂ alkyl alcohol group or an acid-labile C₄-C₁₂ ester group. For example, R₇ may be a 2-hydroxyhexafluoroisopropyl group, a t-butoxycarbonyloxyhexafluoroisopropyl group, or a 2-hydroxytrifluoroisopropyl group.

Alternatively, the photosensitive polymer according to the second embodiment of the present invention may have a structure of formula 16 below:

where n is 0 or 1; R₂ is a substituted or unsubstituted C₁-C₅ hydrocarbon group; R₅ a is hydrogen atom, a methyl group, or a trifluoromethyl group; R₆ is a hydrogen atom or a substituted or unsubstituted C₁-C₂₀ hydrocarbon group; and R₈ is a hydrogen atom, a hydroxyl group, a nitrile group, a substituted or unsubstituted C₁-C₁₂ alkyl group, a fluorinated C₁-C₁₂ alkyl group, an alkoxy group, or an ester group. Preferably, R₆ is a C₄-C₁₂ acid-labile group, and more preferably, a t-butyl group. Preferably, R₈ is a fluorinated C₃-C₁₀ alkyl alcohol group. For example, R₈ may be a 2-hydroxyhexafluoroisopropyl group.

Alternatively, the photosensitive polymer according to the second embodiment of the present invention may have a structure of formula 17 below:

where n is 0 or 1; R₂ is a substituted or unsubstituted C₁-C₅ hydrocarbon group; R₅ is a hydrogen atom, a methyl group, or a trifluoromethyl group; R₆ is a hydrogen atom or a substituted or unsubstituted C₁-C₂₀ hydrocarbon group; and R₇ is a hydrogen atom, a hydroxyl group, a nitrile group, a substituted or unsubstituted C₁-C₁₂ alkyl group, a fluorinated C₁-C₁₂ alkyl group, an alkoxy group, or an ester group. Preferably, R₆ is a C₄-C₁₂ acid-labile group, and more preferably, a t-butyl group. Preferably, R₇ is a fluorinated C₃-C₁₀ alkyl alcohol group or an acid-labile C₄-C₁₂ ester group. For example, R₇ may be a 2-hydroxyhexafluoroisopropyl group, a t-butoxycarbonyloxyhexafluoroisopropyl group, or a 2-hydroxytrifluoroisopropyl group.

Alternatively, the photosensitive polymer according to the second embodiment of the present invention may have a structure of formula 18 below:

where n is 0 or 1; R₂ is a substituted or unsubstituted C₁-C₅ hydrocarbon group; R₅ and R₉, independent of one another, may be a hydrogen atom, a methyl group, or a trifluoromethyl group; R₆ and R₁₀, independent of one another, may be a hydrogen atom or a substituted or unsubstituted C₁-C₂₀ hydrocarbon group; and R₇ is a hydrogen atom, a hydroxyl group, a nitrile group, a substituted or unsubstituted C₁-C₁₂ alkyl group, a fluorinated C₁-C₁₂ alkyl group, an alkoxy group, or an ester group. Preferably, either R₆ or R₁₀ is a C₄-C₁₂ acid-labile group, and more preferably, a t-butyl group. Preferably, R₇ is a fluorinated C₃-C₁₀ alkyl alcohol group or an acid-labile C₄-C₁₂ ester group. For example, R₇ may be a 2-hydroxyhexafluoroisopropyl group, a t-butoxycarbonyloxyhexafluoroisopropyl group, or a 2-hydroxytrifluoroisopropyl group.

Alternatively, the photosensitive polymer according to the second embodiment of the present invention may have a structure of formula 19 below:

where n is 0 or 1; R₃ is a substituted or unsubstituted C₁-C₅ hydrocarbon group; R₅ is a hydrogen atom, a methyl group, or a trifluoromethyl group; R₆ is a hydrogen atom or a substituted or unsubstituted C₁-C₂₀ hydrocarbon group; and R₇ is a hydrogen atom, a hydroxyl group, a nitrile group, a substituted or unsubstituted C₁-C₁₂ alkyl group, a fluorinated C₁-C₁₂ alkyl group, an alkoxy group, or an ester group. Preferably, R₆ is a C₄-C₁₂ acid-labile group, and more preferably, a t-butyl group. Preferably, R₇ is a fluorinated C₃-C₁₀ alkyl alcohol group or an acid-labile C₄-C₁₂ ester group. For example, R₇ may be a 2-hydroxyhexafluoroisopropyl group, a t-butoxycarbonyloxyhexafluoroisopropyl group, or a 2-hydroxytrifluoroisopropyl group.

Alternatively, the photosensitive polymer according to the second embodiment of the present invention may have a structure of formula 20 below:

where R₄ is a substituted or unsubstituted C₁-C₅ hydrocarbon group; R₅ is a hydrogen atom, a methyl group, or a trifluoromethyl group; and R₆ is a hydrogen atom or a substituted or unsubstituted C₁-C₂₀ hydrocarbon group. Preferably, R₆ is a C₄-C₁₂acid-labile group, and more preferably, a t-butyl group.

Alternatively, the photosensitive polymer according to the second embodiment of the present invention may have a structure of formula 21 below:

where R₅ is a hydrogen atom, a methyl group, or a trifluoromethyl group; and R₆ is a hydrogen atom or a substituted or unsubstituted C₁-C₂₀ hydrocarbon group. Preferably, R₆ is a C₄-C₁₂ acid-labile group, and more preferably, a t-butyl group.

Alternatively, the photosensitive polymer according to the second embodiment of the present invention may have a structure of formula 22 below:

where R₅ is a hydrogen atom, a methyl group, or a trifluoromethyl group; R₆ is a hydrogen atom or a substituted or unsubstituted C₁-C₂₀ hydrocarbon group; and R₈ is a hydrogen atom, a hydroxyl group, a nitrile group, a substituted or unsubstituted C₁-C₁₂ alkyl group, a fluorinated C₁-C₁₂ alkyl group, an alkoxy group, or an ester group. Preferably, R₆ is a C₄-C₁₂ acid-labile group, and more preferably, a t-butyl group. Preferably, R₈ is a fluorinated C₃-C₁₀ alkyl alcohol group. For example, R₈ may be a 2-hydroxyhexafluoroisopropyl group.

According to another aspect of the present invention, there is provided a resist composition comprising the photosensitive polymer having one structure of the formulae above and a photoacid generator (PAG).

Preferably, the photoacid generator is contained in an amount of about 1-15% by weight based on the total weight of the photosensitive polymer. Preferably, the photoacid generator comprises triarylsulfonium salts, diaryliodonium salts, sulfonates, or a mixture of these compounds. Suitable examples of the photoacid generator include triphenylsulfonium triflate, triphenylsulfonium antimonate, diphenyliodonium triflate, diphenyliodonium antimonite, methoxydiphenyliodonium triflate, di-t-butyldiphenyliodonium triflate, 2,6-dinitrobenzyl sulfonates, pyrogallol tris(alkylsulfonates), N-hydroxysuccinimide triflate, norbornene-dicarboximide-triflate, triphenylsulfonium nonaflate, diphenyliodonium nonaflate, methoxydiphenyliodonium nonaflate, di-t-butyldiphenyliodonium nonaflate, N-hydroxysuccinimide nonaflate, norbornene-dicarboximide-nonaflate, triphenylsulfonium perfluorooctanesulfonate (PFOS), diphenyliodonium perfluorooctanesulfonate, methoxydiphenyliodonium perfluorooctanesulfonate, di-t-butyldiphenyliodonium triflate, N-hydroxysuccinimide perfluorooctanesulfonate, norbornene-dicarboximide perfluorooctanesulfonate, or a mixture of these compounds.

It is preferable that the resist composition according to an embodiment of the present invention further comprises an organic base. In this case, the organic base may be contained in an amount of about 0.01-2.0% by weight based on the total weight of the photosensitive polymer. Preferably, the organic base comprises a single tertiary amine compound or a mixture of at least two ternary amine compounds. For example, the organic base may be triethylamine, triisobutylamine, triisooctylamine, triisodecylamine, diethanolamine, triethanolamine, or a mixture of these compounds.

It is preferable that the resist composition according to an embodiment of the present invention further comprises a surfactant of about 30-200 ppm.

It is preferable that the resist composition according to an embodiment of the present invention further comprises a dissolution inhibitor of about 0.1-50% by weight based on the total weight of the photosensitive polymer.

A photosensitive polymer according to an embodiment of the present invention contains relatively more fluorine atoms and has a hydrate structure with a number of hydrophilic groups, for example, hydroxyl groups. Thus, a resist composition derived from the polysensitive polymer according to the present invention provides good adhesion to an underlayer and high transmittance at a F₂ excimer laser wavelength of 157 nm. The photosensitive polymer according to an embodiment of the present invention has an appropriate glass transition temperature in the range of about 120-180° C., and the resist composition according to the present invention derived from the photosensitive polymer allows development using conventional developers. Therefore, the resist composition according to the present invention shows excellent lithography performance when applied to a photolithography process using a F₂ excimer laser of 157 nm, and thus is expected to be useful in the manufacture of next generation semiconductor devices.

DETAILED DESCRIPTION OF [THE INVENTION] PREFERRED EMBODIMENTS SYNTHESIS EXAMPLE 1

Synthesis of Monomer

70 g hexafluoroisopropyl alcohol was dissolved in 350 mL dry tetrahydrofuran (THF), followed by dropwise addition of 350 mL 2.5M n-butyllithium for 30 minutes at −70° C. in a nitrogen atmosphere. After stirring for 10 minutes at −70° C., the temperature was elevated in a 0° C.-ice bath. After stirring for additional 1 hour, 53 g of 5-norbornene-2-carboxaldehyde was dropwise added into the solution and stirred at 0° C. for 2 hours. After neutralization with 450 mL a 1 M aqueous solution of hydrochloric acid, the organic phase was separated. The organic layer was diluted with 500 mL of ethylacetate and washed with 500 mL of a saturated aqueous solution of NaCl. The aqueous phase was extracted with 500 mL of ethylacetate. After drying the isolated organic phase with anhydrous MgSO₄, the ethylacetate was distilled under reduced pressure. The remaining product was subjected to column chromatography by using a 1:3 mixture of ethylacetate and hexane by volume as a solvent. Recrystallization at a low temperature following solvent removal resulted 1-bicyclo[2.2.1]hept-5-ene-2-yl-2,2,4,4,4-pentafluoro-butan-1,3,3-triol with a yield of 51%.

SYNTHESIS EXAMPLE 2

Synthesis of Monomer

The procedures of Synthesis Example 1 were followed except that 8-aldehydotetracyclo[4.4.0.1^(2.51).1^(7.10)]dodec-3-ene was used instead of 5-norbornene-2-carboxaldehyde, to synthesize tetracyclo[4.4.0.1^(2.5).1^(7.10)]dodec-3-enyl-2,2,4,4,4-pentafluoro-butan-1,3,3-triol with a yield of 58%.

SYNTHESIS EXAMPLE 3

Synthesis of Monomer

The procedures of Synthesis Example 1 were followed except that pent-4-enal was used instead of 5-norbornene-2-carboxaldehyde, to synthesize 1,1,1,3,3-pentafluoro-non-8-ene-2,2,4-triol with a yield of 78%.

SYNTHESIS EXAMPLE 4

Synthesis of Monomer

The procedures of Synthesis Example 1 were followed except that (4-vinyl-phenyl)-acetaldehyde was used instead of 5-norbornene-2-carboxaldehyde, to synthesize 1,1,1,3,3-pentafluoro-5-(4-vinyl-phenyl)-pentane-2,2,4-triol with a yield of 75%.

SYNTHESIS EXAMPLE 5

Synthesis of Monomer

The procedures of Synthesis Example 1 were followed except that 4-vinylbenzaldehyde was used instead of 5-norbornene-2-carboxaldehyde, to synthesize 2-trifluoromethyl-2-hydroxy-3,3-difluoro-4-phenyloxyethane with a yield of 71%.

Example 1

Synthesis of Polymer

2.9 g 1-bicyclo[2.2.1]hept-5-ene-2-yl-2,2,4,4,4,-pentafluoro-butane-1,3,3,-triol, 4 g 2-trifluoromethyl-acrylic acid t-butyl ester, 2.8 g 2-bicyclo[2.2.1]hept-5-ene-2-ylmethyl-1,1,1,3,3,3-hexafluoro-propan-2-ol, 0.34 g 1,6-hexandiol divinylether, and 0.6 g azobisisobutyronitrile (AlBN) were reacted at 65° C. for 24 hours. The resultant reaction product was precipitated twice in excess hexane and filtered. The filtrate was dried in a vacuum oven for 24 hours to recover a polymer having a desired structure with a yield of 58%.

The resultant polymer had an average molecular weight (Mw) of 15,400 and a polydispersity (Mw/Mn) of 13.4.

Example 2

Synthesis of Polymer

2.1 g 1-bicyclo[2.2.1]hept-5-ene-2-yl-2,2,4,4,4,-pentafluoro-butan-1,3,3,-triol, 3 g 2-trifluoromethyl-acrylic acid t-butyl ester, 1.5 g 1,1,1-trifluoro-2-(4-vinyl-phenyl)-propan-2-ol, 0.42 g AlBN were degassed and reacted at 65° C. for 24 hours. The resultant reaction product was precipitated twice in excess hexane and filtered. The filtrate was dried in a vacuum oven for 24 hours to recover a polymer having a desired structure with a yield of 72%.

The resultant polymer had an average molecular weight (Mw) of 22,000 and a polydispersity (Mw/Mn) of 1.5.

Example 3

Synthesis of Polymer

2.7 g 1-bicyclo[2.2.1]hept-5-ene-2-yl-2,2,4,4,4,-pentafluoro-butan-1,3,3,-triol, 1.8 g 2-trifluoromethyl-acrylic acid t-butyl ester, 2.5 g 1,1,1,3,3,3-hexafluoro-2-(4-vinyl-phenyl)-propan-2-ol, and 0.24 g AlBN were degassed and reacted at 65° C. for 24 hours. The resultant reaction product was precipitated twice in excess hexane and filtered. The filtrate was dried in a vacuum oven for 24 hours to recover a polymer having a desired structure with a yield of 71%.

The resultant polymer had an average molecular weight (Mw) of 29,000 and a polydispersity (Mw/Mn) of 1.7.

Example 4

Synthesis of Polymer

2.1 g 1-bicyclo[2.2.1]hept-5-ene-2-yl-2,2,4,4,4,-pentafluoro-butan-1,3,3,-triol, 3 g 2-trifluoromethyl-acrylic acid t-butyl ester, 2.4 g carbonic acid t-butyl ester 2,2,2-trifluoro-1-trifluoromethyl-1-(4-vinyl-phenyl)-ethyl ester, and 0.42 g AlBN were degassed and reacted at 65° C. for 24 hours. The resultant reaction product was precipitated twice in excess hexane and filtered. The filtrate was dried in a vacuum oven for 24 hours to recover a polymer having a desired structure with a yield of 66%.

The resultant polymer had an average molecular weight (Mw) of 28,000 and a polydispersity (Mw/Mn) of 1.7.

Example 5

Synthesis of Polymer

3.5 g 1-bicyclo[2.2.1]hept-5-ene-2-yl-2,2,4,4,4,-pentafluoro-butan-1,3,3,-triol, 2.4 g 2-trifluoromethyl-acrylic acid t-butyl ester, 3.2 g carbonic acid t-butyl ester 2,2,2-trifluoro-1-trifluoromethyl-1-(4-vinyl-phenyl)-ethyl ester, 0.15 g trifluoromethacrylic acid, and 0.48 g AlBN were degassed and reacted at 65° C. for 24 hours. The resultant reaction product was precipitated twice in excess hexane and filtered. The filtrate was dried in a vacuum oven for 24 hours to recover a polymer having a desired structure with a yield of 65%.

The resultant polymer had an average molecular weight (Mw) of 26,900 and a polydispersity (Mw/Mn) of 2.52.

Example 6

Synthesis of Polymer

2.6 g tetracyclo[4.4.0.1^(2.5).1^(7.10)]dodec-3-enyl-2,2,4,4,4-pentafluoro-butan-1,3,3-triol, 3 g 2-trifluoromethyl-acrylic acid t-butyl ester, 2 g 1,1,1,3,3,3-hexafluoro-2-(4-vinyl-phenyl)-propan-2-ol, and 0.42 g AlBN were degassed and reacted at 65° C. for 24 hours. The resultant reaction product was precipitated twice in excess hexane and filtered. The filtrate was dried in a vacuum oven for 24 hours to recover a polymer having a desired structure with a yield of 61%.

The resultant polymer had an average molecular weight (Mw) of 27,000 and a polydispersity (Mw/Mn) of 1.8.

Example 7

Synthesis of Polymer

2.6 g tetracyclo[4.4.0.1^(2.5).1^(7.10)]dodec-3-enyl-2,2,4,4,4-tentafluoro-butan-1,3,3-triol, 3 g 2-trifluoromethyl-acrylic acid t-butyl ester, 2.4 g carbonic acid t-butyl ester 2,2,2-trifluoro-1-trifluoromethyl-1-(4-vinyl-phenyl)-ethyl ester, and 0.42 g AlBN were degassed and reacted at 65° C. for 24 hours. The resultant reaction product was precipitated twice in excess hexane and filtered. The filtrate was dried in a vacuum oven for 24 hours to recover a polymer having a desired structure with a yield of 56%.

The resultant polymer had an average molecular weight (Mw) of 24,000 and a polydispersity (Mw/Mn) of 1.9.

Example 8

Synthesis of Polymer

3.9 g 1,1,1,3,3,-pentafluoro-non-8-ene-2,2,4-triol, 3 g 2-trifluoromethyl-acrylic acid t-butyl ester, 4.0 g 1,1,1-trifluoro-2-(4-vinyl-phenyl)-propan-2-ol, and 0.36 g AlBN were degassed and reacted at 65° C. for 24 hours. The resultant reaction product was precipitated twice in excess hexane and filtered. The filtrate was dried in a vacuum oven for 24 hours to recover a polymer having a desired structure with a yield of 58%.

The resultant polymer had an average molecular weight (Mw) of 27,000 and a polydispersity (Mw/Mn) of 2.1.

Example 9

Synthesis of Polymer

2.8 g 2-trifluoromethyl-2-hydroxy-3,3-difluoro 4-phenyloxyethane, 2 g 2-trifluoromethyl-acrylic acid t-butyl ester, and 0.16 g AlBN were dissolved in 5 g ethylacetate, degassed, and polymerized at 65° C. for 24 hours.

The resultant polymer had an average molecular weight (Mw) of 25,200 and a polydispersity (Mw/Mn) of 2.6.

Example 10

Synthesis of Polymer

4.6 g 1,1,1,3,3-pentafluoro-5-(4-vinyl-phenyl)-pentane-2,2,4-triol, 3 g 2-trifluoromethyl-acrylic t-butyl ester, and 0.24 g AlBN were dissolved in 5 g ethylacetate, degassed, and polymerized at 65° C. for 24 hours. The resultant reaction product was precipitated twice in excess hexane and filtered. The filtrate was dried in a vacuum oven for 24 hours to recover a polymer having a desired structure with a yield of 71%.

The resultant polymer had an average molecular weight (Mw) of 28,000 and a polydispersity (Mw/Mn) of 2.4.

Example 11

Synthesis of Polymer

2.8 g 2-trifluoromethyl-2-hydroxy-3,3-difluoro 4-phenyloxyethane, 2 g 2-trifluoromethyl-acrylic acid t-butyl ester, 1.3 g 2-bicyclo[2.2.1]hept-5-ene-2-ylmethyl-1,1,1,3,3,3-hexafluoro-propan-2-ol, and 0.24 g AlBN were dissolved in 3 g ethylacetate, degassed, and polymerized at 65° C. for 24 hours.

The resultant polymer had an average molecular weight (Mw) of 26,400 and a polydispersity (Mw/Mn) of 2.3.

Example 12

Preparation of Resist Composition

1.0 g of each of the polymers synthesized in Examples 1 through 11 was dissolved in 15 g cyclohexanon together with 0.05 g triphenylsulfonium trifluoromethanesulfonate (triflate) as a photoacid generator (PAG) and 5 mg triisodecylamine as an organic base. Each mixed solution was filtered through a 0.2-μm-membrane filter to obtain a resist composition. Each of the resist compositions was coated on a silicon wafer having an organic anti-reflective coating (ARC) to a thickness of about 0.15 μm.

Each of the wafers coated with different resist compositions was soft-baked at a temperature of 100-140° C. for 60 seconds and exposed using an F₂ excimer laser stepper (NA=0.6). After the exposure process, the wafer was subjected to post-exposure bake (PEB) at a temperature of 110-140° C. for 60 seconds. The resultant wafer was subjected to development with a 2.38% by weight tetramethylammonium hydroxide (TMAH) solution, to form a resist pattern.

As a result, a pattern of lines and spaces of 0.08-0.23 μm was obtained at an exposure dose of about 5-60 mJ/cm².

Evaluation Example

Measurement of pKa Value

To determine whether a repeating monomer unit of a polymer according to the present invention has a structure dissolvable in common developers, pKa value was measured.

The pKa value was measured for a variety of monomers having different structures to identify whether hydrate is dissolvable in developers. The results are shown in Table 1.

TABLE 1 MONOMER 1 MONOMER 2 MONOMER 3 MONOMER 4 MONOMER 5 MONOMER 6

pKa = 15.24 pKa = 9.97 pKa = 4.58 pKa = 9.67 pKa = 8.96 pKa = 8.33

As shown in Table 1, vinylphenol (monomer 2 of Table 1) for KrF resist compositions has a pKa value of 9.97, a methylmethacarboxylic acid structure (monomer 3 of Table 1) for ArF resist compositions has a pKa value of 4.58. Hexafluoroisopropanols (monomers 4 and 5 of Table 1) have a pKa of 9.67 and 8.96, respectively, which are slightly different due to their substitute groups but are similar to that from phenol. Those levels of acidity of monomers 4 and 5 are due to a trifluoromethyl group at the α-carbon position of the hydroxyl (—OH) group acting as a strong electron withdrawer for taking H⁺ ions from the hydroxyl group.

A monomer (monomer 6 of Table 1) forming a repeating unit of a polymer according to the present invention has a relatively low pKa value of 8.33. From this result, the polymer according to the present invention is expected to more easily react with an alkaline developer.

A photosensitive polymer according to an embodiment of the present invention contains more fluorine atoms and has a hydrate structure with a number of hydrophilic groups, such as a hydroxyl group. A photosensitive polymer according to an embodiment of the present invention with three hydroxyl groups can enhance hydrophilicity of a resist composition prepared therefrom. Therefore, the resist composition prepared with the photosensitive polymer according to an embodiment of the present invention exhibits good adhesion to an underlayer. Since the photosensitive polymer according to an embodiment of the present invention contains a number of fluorine atoms, its transmittance with respect to an F₂ excimer laser having a short wavelength (e.g.,157 nm) is great. Therefore, when a resist layer formed of the resist composition according to the present invention is patterned into a pattern of lines, the resulting pattern shows little lines with rough edges.

The photosensitive polymer according to the present invention has an appropriate glass transition temperature of about 120-180° C. A resist layer formed of a resist composition containing the photosensitive polymer according to the present invention is sufficiently annealed during a baking process, thereby resulting a reduced free volume in the resist layer. Accordingly, stability of the resist layer against environmental conditions is improved even when post-exposure delay occurs. The resist composition according to the present invention is applicable with general developers. The resist composition according to the present invention shows excellent lithography performance when applied to a lithography process using an F₂ excimer laser of 157 nm, with the expectation of effectiveness in the manufacture of next generation semiconductor devices.

While this invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. 

What is claimed is:
 1. A photosensitive polymer having an average molecular weight of about 3,000-100,000 with a repeating unit including a group of one of the following structural formulae:


2. The photosensitive polymer of claim 1, wherein the repeating unit has a structural formula:

where n is 0 or 1, and R₁ is a substituted or unsubstituted C₁-C₅ hydrocarbon group.
 3. The photosensitive polymer of claim 1, wherein the repeating unit has a structural formula:

where n is 0 or 1, and R₂ is a substituted or unsubstituted C₁-C₅ hydrocarbon group.
 4. The photosensitive polymer of claim 1, wherein the repeating unit has a structural formula:

where n is 0 or 1, and R₃ is a substituted or unsubstituted C₁-C₅ hydrocarbon group.
 5. The photosensitive polymer of claim 1, wherein the repeating unit has a structural formula:

where R₄ is a substituted or unsubstituted C₁-C₅ hydrocarbon group.
 6. The photosensitive polymer of claim 1, wherein the repeating unit has a structural formula:


7. A photosensitive polymer having an average molecular weight of about 3,000-100,000 with a first repeating unit selected from the group of one of the following structural formulae:

and at least one second repeating unit [(b)] selected from the group consisting of acrylate, methacrylate, maleic anhydride, norbornene, styrene, tetrafluoroethylene, and sulfur dioxide derivatives.
 8. The photosensitive polymer of claim 7 having a structural formula:

where n is 0 or 1; R₁ is a substituted or unsubstituted C₁-C₅ hydrocarbon group; R₅ is a hydrogen atom, a methyl group, or a trifluoromethyl group; R₆ is a hydrogen atom or a substituted or unsubstituted C₁-C₂₀ hydrocarbon group; and R₇ is a hydrogen atom, a hydroxyl group, a nitrile group, a substituted or unsubstituted C₁-C₁₂ alkyl group, a fluorinated C₁-C₁₂ alkyl group, an alkoxy group, or an ester group.
 9. The photosensitive polymer of claim 8, wherein R₆ is a C₄-C₁₂ acid-labile group.
 10. The photosensitive polymer of claim 9, wherein R₆ is a t-butyl group.
 11. The photosensitive polymer of claim 8, wherein R₇ is a fluorinated C₃-C₁₂ alkyl alcohol group.
 12. The photosensitive polymer of claim 8, wherein R₇ is an acid labile C₄-C₁₂ ester group.
 13. The photosensitive polymer of claim 8, wherein R₇ is a 2-hydroxyhexafluoroisopropyl group, a t-butoxycarbonyloxyhexafluoroisopropyl group, or a 2-hydroxytrifluoroisopropyl group.
 14. The photosensitive polymer of claim 7 having a structural formula:

where n is 0 or 1; R₂ is a substituted or unsubstituted C₁-C₅ hydrocarbon group; R₅ is a hydrogen atom, a methyl group, or a trifluoromethyl group; R₆ is a hydrogen atom or a substituted or unsubstituted C₁-C₂₀ hydrocarbon group; and R₈ is a hydrogen atom, a hydroxyl group, a nitrile group, a substituted or unsubstituted C₁-C₁₂ alkyl group, a fluorinated C₁-C₁₂ alkyl group, an alkoxy group, or an ester group.
 15. The photosensitive polymer of claim 14, wherein R₆ is a C₄-C₁₂ acid-labile group.
 16. The photosensitive polymer of claim 15, wherein R₆ is a t-butyl group.
 17. The photosensitive polymer of claim 14, wherein R₈ is a fluorinated C₃-C₁₀ alkyl alcohol group.
 18. The photosensitive polymer of claim 14, wherein R₈ is a 2-hydroxyhexafluoroisopropyl group.
 19. The photosensitive polymer of claim 7 having a structural formula:

where n is 0 or 1; R₂ is a substituted or unsubstituted C₁-C₅ hydrocarbon group; R₅ is a hydrogen atom, a methyl group, or a trifluoromethyl group; R₆ is a hydrogen atom or a substituted or unsubstituted C₁-C₂₀ hydrocarbon group; and R₇ is a hydrogen atom, a hydroxyl group, a nitrile group, a substituted or unsubstituted C₁-C₁₂ alkyl group, a fluorinated C₁-C₁₂ alkyl group, an alkoxy group, or an ester group.
 20. The photosensitive polymer of claim 19, wherein R₆ is a C₄-C₁₂ acid-labile group.
 21. The photosensitive polymer of claim 20, wherein R₆ is a t-butyl group.
 22. The photosensitive polymer of claim 19, wherein R₇ is a fluorinated C₃-C₁₀ alkyl alcohol group.
 23. The photosensitive polymer of claim 19, wherein R₇ is an acid-labile C₄-C₁₂ ester group.
 24. The photosensitive polymer of claim 19, wherein R₇ is a 2-hydroxyhexafluoroisopropyl group, a t-butoxycarbonyloxyhexafluoroisopropyl group, or a 2-hydroxytrifluoroisopropyl group.
 25. The photosensitive polymer of claim 7 having a structural formula:

where n is 0 or 1; R₂ is a substituted or unsubstituted C₁-C₅ hydrocarbon group; R₅ and R₉, independent of one another, may be a hydrogen atom, a methyl group, or a trifluoromethyl group; R₆ and R₁₀, independent of one another, may be a hydrogen atom or a substituted or unsubstituted C₁-C₂₀ hydrocarbon group; and R₇ is a hydrogen atom, a hydroxyl group, a nitrile group, a substituted or unsubstituted C₁-C₁₂ alkyl group, a fluorinated C₁-C₁₂ alkyl group, an alkoxy group, or an ester group.
 26. The photosensitive polymer of claim 25, wherein at least one of R₆ and R₁₀ is a C₄-C₁₂ acid-labile group.
 27. The photosensitive polymer of claim 26, wherein at least one of R₆ and R₁₀ is a t-butyl group.
 28. The photosensitive polymer of claim 25, wherein R₇ is a fluorinated C₃-C₁₀ alkyl alcohol group.
 29. The photosensitive polymer of claim 25, wherein R₇ is an acid-labile C₄-C₁₂ ester group.
 30. The photosensitive polymer of claim 25, wherein R₇ is a 2-hydroxyhexafluoroisopropyl group, a t-butoxycarbonyloxyhexafluoroisopropyl group, or a 2-hydroxytrifluoroisopropyl group.
 31. The photosensitive polymer of claim 7 having a structural formula:

where n is 0 or 1; R₃ is a substituted or unsubstituted C₁-C₅ hydrocarbon group; R₅ is a hydrogen atom, a methyl group, or a trifluoromethyl group; R₆ is a hydrogen atom or a substituted or unsubstituted C₁-C₂₀ hydrocarbon group; and R₇ is a hydrogen atom, a hydroxyl group, a nitrile group, a substituted or unsubstituted C₁-C₁₂ alkyl group, a fluorinated C₁-C₁₂ alkyl group, an alkoxy group, or an ester group.
 32. The photosensitive polymer of claim 31, wherein R₆ is a C₄-C₁₂ acid labile group.
 33. The photosensitive polymer of claim 32, wherein R₆ is a t-butyl group.
 34. The photosensitive polymer of claim 31, wherein R₇ is a fluorinated C₃-C₁₀ alkyl alcohol group.
 35. The photosensitive polymer of claim 31, wherein R₇ is an acid-labile C₄-C₁₂ ester group.
 36. The photosensitive polymer of claim 31, wherein R₇ is a 2-hydroxyhexafluoroisopropyl group, a t-butoxycarbonyloxyhexafluoroisopropyl group, or a 2-hydroxytrifluoroisopropyl group.
 37. The photosensitive polymer of claim 7 having a structural formula:

where R₄ is a substituted or unsubstituted C₁-C₅ hydrocarbon group; R₅ is a hydrogen atom, a methyl group, or a trifluoromethyl group; and R₆ is a hydrogen atom or a substituted or unsubstituted C₁-C₂₀ hydrocarbon group.
 38. The photosensitive polymer of claim 37, wherein R₆ is a C₄-C₁₂ acid-labile group.
 39. The photosensitive polymer of claim 38, wherein R₆ is a t-butyl group.
 40. The photosensitive polymer of claim 7 having a structural formula:

where R₅ is a hydrogen atom, a methyl group, or a trifluoromethyl group; and R₆ is a hydrogen atom or a substituted or unsubstituted C₁-C₂₀ hydrocarbon group.
 41. The photosensitive polymer of claim 40, wherein R₆ is a C₄-C₁₂ acid-labile group.
 42. The photosensitive polymer of claim 41, wherein R₆ is a t-butyl group.
 43. The photosensitive polymer of claim 7 having a structural formula:

where R₅ is a hydrogen atom, a methyl group, or a trifluoromethyl group; R₆ is a hydrogen atom or a substituted or unsubstituted C₁-C₂₀ hydrocarbon group; and R₈ is a hydrogen atom, a hydroxyl group, a nitrile group, a substituted or unsubstituted C₁-C₁₂ alkyl group, a fluorinated C₁-C₁₂ alkyl group, an alkoxy group, or an ester group.
 44. The photosensitive polymer of claim 43, wherein R₆ is a C₄-C₁₂ acid-labile group.
 45. The photosensitive polymer of claim 44, wherein R₆ is a t-butyl group.
 46. The photosensitive polymer of claim 43, wherein R₈ is a fluorinated C₃-C₁₀ alkyl alcohol group.
 47. The photosensitive polymer of claim 43, wherein R₈ is a 2-hydroxyhexafluoroisopropyl group.
 48. A resist composition comprising: the photosensitive polymer of any one of claims 1 through 47; and a photoacid generator (PAG).
 49. The resist composition of claim 48, wherein the photoacid generator is contained in an amount of about 1-15% by weight based on the total weight of the photosensitive polymer.
 50. The resist composition of claim 48, wherein the photoacid generator comprises triarylsulfonium salts, diaryliodonium salts, sulfonates, or a mixture of these compounds.
 51. The resist composition of claim 48, wherein the photoacid generator comprises triphenylsulfonium triflate, triphenylsulfonium antimonate, diphenyliodonium triflate, diphenyliodonium antimonite, methoxydiphenyliodonium triflate, di-t-butyldiphenyliodonium triflate, 2,6-dinitrobenzyl sulfonates, pyrogallol tris(alkylsulfonates), N-hydroxysuccinimide triflate, norbornene-dicarboximide-triflate, triphenylsulfonium nonaflate, diphenyliodonium nonaflate, methoxydiphenyliodonium nonaflate, di-t-butyldiphenyliodonium nonaflate, N-hydroxysuccinimide nonaflate, norbornene-dicarboximide-nonaflate, triphenylsulfonium perfluorooctanesulfonate (PFOS), diphenyliodonium perfluorooctanesulfonate, methoxydiphenyliodonium perfluorooctanesulfonate, di-t-butyldiphenyliodonium triflate, N-hydroxysuccinimide perfluorooctanesulfonate, norbornene-dicarboximide perfluorooctanesulfonate, or a mixture of these compounds.
 52. The resist composition of claim 48, further comprising an organic base.
 53. The resist composition of claim 52, wherein the organic base is contained in an amount of about 0.01-2.0% by weight based on the total weight of the photosensitive polymer.
 54. The resist composition of claim 52, wherein the organic base comprises a single tertiary amine compound or a mixture of at least two ternary amine compounds.
 55. The resist composition of claim 52, wherein the organic base comprises triethylamine, triisobutylamine, triisooctylamine, triisodecylamine, diethanolamine, triethanolamine, or a mixture of these compounds.
 56. The resist composition of claim 48, further comprising a surfactant of about 30-200 ppm.
 57. The resist composition of claim 48, further comprising a dissolution inhibitor of about 0.1-50% by weight based on the total weight of the photosensitive polymer. 